The timing of puberty and vaginal opening (VO) in rats can be greatly altered by under or over-feeding. It is possible that these nutritional states influence puberty by altering the glucose uptake and function of insulin-sensitive cells of the ventro medial hypothalamus (VMH), an area of the brain intimately concerned with the regulation of puberty and ovarian function and with the control and monitoring of nutrient homeostasis. To test this hypothesis (1) effects of under-and over-feeding upon prepubertal glucose metabolism and VO will be examined (2) effects of VMH implants of insulin or glucose upon VO will be studied (3) hypothalamic glucose uptake at various ages before and after puberty will be studied through the use of goldthioglucose (4) effects of over- and under-feeding upon ovarian responsiveness to human chorionic gonadotropin will be determined, and (5) effects of VMH implants of insulin upon the negative feedback control of LH by estradiol will be studied.